Disinfection and Sterilization Methods and Controversies

DISINFECTION AND STERILIZATION:
ABINAYA ARMUGAM
GROUP: 25

Copyright © 2004 WA Rutala
DISINFECTION AND STERILIZATION:
ISSUES AND CONTROVERSIES
Methods in Disinfection
 Endoscopes/AERs, endocavitary probes,
emerging pathogens
Methods in Sterilization
 CJD
Issues and Controversies
 Surface disinfection, CJD, glutaraldehyde
exposure time (45m/25oC vs 20m/20oC),
endoscope rinse water

DISINFECTION/STERILIZATION
INFLUENCING FACTORS
Cleaning of the object
Organic and inorganic load present
Type and level of microbial contamination
Concentration of and exposure time to disinfectant/sterilant
Nature of the object
Temperature and relative humidity

DECREASING ORDER OF RESISTANCE OF
MICROORGANISMS TO DISINFECTANTS/STERILANTS
Prions
Spores
Mycobacteria
Non-Enveloped Viruses
Fungi
Bacteria
Enveloped Viruses

DISINFECTION AND
STERILIZATION
EH Spaulding believed that how an object will be
disinfected depended on the object’s intended use.
CRITICAL - objects which enter normally sterile tissue or
the vascular system or through which blood flows
should be sterile.
SEMICRITICAL - objects that touch mucous
membranes or skin that is not intact require a
disinfection process (high-level disinfection[HLD])
that kills all microorganisms but high numbers of
bacterial spores.
NONCRITICAL -objects that touch only intact skin
require low-level disinfection.

PROCESSING “CRITICAL” PATIENT CARE
OBJECTS
Classification: Critical objects enter normally
sterile tissue or vascular system, or
through which blood flows.
Object: Sterility.
Level germicidal action: Kill all microorganisms,
including bacterial spores.
Examples: Surgical instruments and devices;
cardiac catheters; implants; etc.
Method: Steam, gas, hydrogen peroxide
plasma or chemical sterilization.

CRITICAL OBJECTS
Surgical instruments
Cardiac catheters
Implants

CHEMICAL STERILIZATION OF “CRITICAL
OBJECTS”
Glutaraldehyde (> 2.0%)
Hydrogen peroxide-HP (7.5%)
Peracetic acid-PA (0.2%)
HP (1.0%) and PA (0.08%)
HP (7.5%) and PA (0.23%)
Glut (1.12%) and Phenol/phenate (1.93%)
__________________________________________
_____
Exposure time per manufacturers’ recommendations

PROCESSING “SEMICRITICAL”
PATIENT CARE OBJECTS
Classification: Semicritical objects come in contact
with mucous membranes or skin that
is not intact.
Object: Free of all microorganisms except
high numbers of bacterial spores.
Level germicidal action: Kills all microorganisms except
high numbers of bacterial spores.
Examples: Respiratory therapy and anesthesia
equipment, GI endoscopes,
thermometer, etc.
Method: High-level disinfection

SEMICRITICAL ITEMS
Endoscopes
Respiratory therapy equipment
Anesthesia equipment
Endocavitary probes
Tonometers
Diaphragm fitting rings

PROCESSING “NONCRITICAL”
PATIENT CARE OBJECTS
Classification: Noncritical objects will not come in
contact with mucous membranes or
skin that is not intact.
Object: Can be expected to be contaminated
with some microorganisms.
Level germicidal action: Kill vegetative bacteria, fungi and
lipid viruses.
Examples: Bedpans; crutches; bed rails; EKG
leads; bedside tables; walls, floors and
furniture.
Method: Low-level disinfection

LOW-LEVEL DISINFECTION FOR
“NONCRITICAL” OBJECTS
Exposure time > 1 min
Germicide Use Concentration
Ethyl or isopropyl alcohol 70-90%
Chlorine 100ppm (1:500 dilution)
Phenolic UD
Iodophor UD
Quaternary ammonium UD
_____________________________________
UD=Manufacturer’s recommended use dilution

DISINFECTANTS FOR SURFACE DISINFECTION
CONTROVERSY
 Noncritical Surfaces
 Medical equipment surfaces (BP cuff, stethoscopes)
 May frequently become contaminated with patient material
 Repeatedly touched by health care personnel
 Disinfectant/detergent should be used
 Housekeeping surfaces (bed rails, bedside tables)
 May play a theoretical but less significant role in diseases
transmission
 Disinfectants/detergents may be used (II) and detergents (non-patient
care areas)

NEW FDA-CLEARED STERILANTS
 “Old”
 > 2% Glut, 7.5% HP, 1.0% HP and 0.08% PA
 New
 1.21% glut and 1.93% phenol/phenate (HLD-20 m at
25oC)
 0.55% ortho-phthalaldehyde (HLD-12 m)
 7.35% HP and 0.23% PA (HLD-15 m)
 2.5% Glut (HLD-5 m at 35oC)
 Hypochlorite (650-675ppm free chlorine)
 Ensure antimicrobial activity and material
compatibility

GLUTARALDEHYDE
 Advantages
 Numerous use studies published
 Relatively inexpensive
 Excellent materials compatibility
 Disadvantages
 Respiratory irritation from vapor
 Pungent and irritating odor
 Relatively slow mycobactericidal activity
 Coagulate blood and fix tissues to surfaces
 Allergic contact dermatitis

ORTHO-PHTHALALDEHYDE
Advantages
 Fast acting HLD
 No activation
 Excellent materials
compatibility
 Not a known irritant to
eyes and nasal passages
 Weak odor
Disadvantages
 Stains protein gray
 Cost ($30/gal);but lower
reprocessing costs-soak
time, devices per gal)
 Slow sporicidal activity
 Eye irritation with contact

COMPARISON OF GLUTARALDEHYDE AND OPA
>2.0% Glutaraldehyde
 HLD: 45 min at 25oC
 Needs activator
 14 day use life
 2 year shelf life
 ACGIH ceiling limit,
0.05ppm
 Strong odor
 MEC, 1.5%
 Cost - $10/gallon
0.55% Ortho-phthalaldehyde
 HLD: 12 min at 20oC
 No activator needed
 14 day use life
 2 year shelf life
 No ACGIH or OSHA limit
 Weak odor
 MEC, 0.3%
 Cost - $30/gallon

ORTHO-PHTHALALDEHYDE (OPA)
NEW CONTRAINDICATIONS FOR OPA
 Repeated exposure to OPA, following manual
reprocessing of urological instruments, may have
resulted in hypersensitivity in some patients with a
history of bladder cancer undergoing repeated
cystoscopy.
 Out of approximately 1 million urological procedures,
there have been reports of 24 patients who have
experience ‘anaphylaxis-like’ reactions after repeated
cystoscopy (typically after 4-9 treatments).
 Risk control measures: residues of OPA minimized;
and contraindicated for reprocessing of urological
instruments used on patients with history of bladder
cancer.

ENDOSCOPE DISINFECTION
 CLEAN-mechanically cleaned with water and
enzymatic cleaner
 HLD/STERILIZE-immerse scope and perfuse
HLD/sterilant through all channels for at least 12
min
 RINSE-scope and channels rinsed with sterile
water, filtered water, or tap water followed by
alcohol
 DRY-use forced air to dry insertion tube and
channels
 STORE-prevent recontamination

RINSE WATER FOR HLD
 Endoscopes-After HLD, rinse endoscopes and flush
channels with sterile water, filtered water, or tapwater
followed by a rinse with 70-90% ethyl or isopropyl alcohol
 Other Semicritical Devices-After HLD, use sterile water,
filtered water, or tapwater followed by an alcohol rinse for
devices that contact upper respiratory tract (II).
 No recommendation for sterile or filtered water versus
tapwater alone for devices that contact mm of rectum or
vagina.

ENDOCAVITARY PROBES
 Probes-Transesophageal echocardiography probes,
vaginal/rectal probes used in sonographic scanning
 Probes with contact with mucous membranes are
semicritical
 Guideline recommends that a new condom/probe cover
should be used to cover the probe for each patient and
since covers may fail (1-80%), HLD (semicritical probes)
should be performed

STERILIZATION
The complete elimination or
destruction of all forms of microbial
life and is accomplished in
healthcare facilities by either
physical or chemical processes

STEAM STERILIZATION
 Advantages
 Non-toxic
 Cycle easy to control and monitor
 Inexpensive
 Rapidly microbicidal
 Least affected by organic/inorganic soils
 Rapid cycle time
 Penetrates medical packing, device lumens
 Disadvantages
 Deleterious for heat labile instruments
 Potential for burns

NEW TRENDS IN STERILIZATION OF PATIENT
EQUIPMENT
 Alternatives to ETO-CFC
ETO-CO2, ETO-HCFC, 100% ETO
 New Low Temperature Sterilization Technology
Hydrogen Peroxide Gas Plasma
Peracetic Acid

ETHYLENE OXIDE (ETO)
 Advantages
 Very effective at killing microorganisms
 Penetrates medical packaging and many plastics
 Compatible with most medical materials
 Cycle easy to control and monitor
 Disadvantages
 Some states (CA, NY, TX) require ETO emission
reduction of 90-99.9%
 CFC (inert gas that eliminates explosion hazard)
banned after 1995
 Potential hazard to patients and staff
 Lengthy cycle/aeration time

HYDROGEN PEROXIDE GAS PLASMA
STERILIZATION
Advantages
 Safe for the environment and health care worker; it
leaves no toxic residuals
 Fast - cycle time is 45-73 min and no aeration necessary
 Used for heat and moisture sensitive items since process
temperature 50oC
 Simple to operate, install, and monitor
 Compatible with most medical devices

HYDROGEN PEROXIDE GAS PLASMA
STERILIZATION
Disadvantages
 Cellulose (paper), linens and liquids cannot be processed
 Sterilization chamber is small, about 3.5ft3 to 7.3ft3
 Endoscopes or medical devices restrictions based on
lumen internal diameter and length (see manufacturer’s
recommendations)
 Requires synthetic packaging (polypropylene) and
special container tray

CONCLUSIONS
 All sterilization processes effective in killing spores
 Cleaning removes salts and proteins and must precede
sterilization
 Failure to clean or ensure exposure of microorganisms to
sterilant (e.g. connectors) could affect effectiveness of
sterilization process

RECOMMENDATIONS
METHODS OF STERILIZATION
 Steam is preferred for critical items not damaged by heat
 Follow the operating parameters recommended by the
manufacturer
 Use low temperature sterilization technologies for
reprocessing critical items damaged by heat
 Use immediately critical items that have been sterilized
by peracetic acid immersion process (no long term
storage)

CJD : potential for secondary
spread through contaminated
surgical instruments

CJD: RECOMMENDATIONS FOR
DISINFECTION AND STERILIZATION
 High risk patient, high risk tissue, critical/semicritical
device-special prion reprocessing
 High risk patient, low/no risk tissue, critical/semicritical
device-conventional D/S or special prion reprocessing
 Low risk patient, high risk tissue, critical/semicritical
device-conventional D/S
 High risk patient, high risk tissue, noncritical device-
conventional disinfection

CJD: DISINFECTION AND STERILIZATION
CONCLUSIONS
 Critical/SC-cleaning with special prion reprocessing
 NaOH and steam sterilization (e.g., 1N NaOH 1h, 121oC 30 m)
 134oC for 18m (prevacuum)
 132oC for 60m (gravity)
 No low temperature sterilization technology effective
 Noncritical-four disinfectants (e.g., chlorine) effective (4
log decrease in LD50 within 1h)

CJD: INSTRUMENT REPROCESSING
 Special prion reprocessing by combination of NaOH and
steam sterilization
 Immerse in 1N NaOH for 1 hour; remove and rinse in water,
then transfer to an open pan and autoclave for 1 hour
 Immerse in 1N NaOH for 1 hour and heat in a gravity
displacement sterilizer at 121oC for 30 minutes
 Combined use of autoclaving in sodium hydroxide has
raised concerns of possible damage to autoclaves, and
hazards to operators due to the caustic vapors.
 Risk can be minimized by the use of polypropylene
containment pans and lids.

CJD: INSTRUMENT REPROCESSING
 Special prion reprocessing by combination of NaOH and
steam sterilization
 Immerse in 1N NaOH for 1 hour; remove and rinse in
water, then transfer to an open pan and autoclave for
1 hour
 Immerse in 1N NaOH for 1 hour and heat in a gravity
displacement sterilizer at 121oC for 30 minutes
 Combined use of autoclaving in sodium hydroxide has
raised concerns of possible damage to autoclaves, and
hazards to operators due to the caustic fumes.
 Risk can be minimized by the use of polypropylene
containment pans and lids (AJIC 2003; 31:257-60).

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